The scientific correspondence of Viereck has been separated from his other papers, alphabetized by author and treated as a special collection.

The carbon copies are filed under the name of the addressee, as are the letterbook copies covering the years 1905-07. The latter contains 200 letters to some 51 persons, bringing the total number written by Viereck to 1,107.

The coverage is entomological, with special stress on Hymenoptera. Papers refer to his early general studies in Philadelphia, his later identification of Hymenoptera for various museums, his collaboration with W. E. Britton in writing the section on hymenoptera for the Insects of New Jersey, his trip to Europe and meeting with foreign entomologists, his stay in Italy, while exploring for the California Horticultural Commission, his contacts while with the U. S. Dept. of Agriculture, and finally to his association with the Canadian Entomological Branch of the Dept. of Agriculture.

Gift of the author; stored for years in the Department of insects; archived in December 1951 and deposited at the American Philosophical Society's library, remaining there until 1959. While under the Society's care, all papers were microfilmed for their library.